Brain connectivity can be determined by outlining the density of white matter tracts between brain regions using diffusion tensor imaging (DTI structural connectivity), or by detecting correlations in brain activation patterns across regions, using functional Magnetic Resonance Imaging (fMRI functional connectivity). In addition to these structural and functional brain characteristics, the question whether connectivity of the socially-anxious brain meets the criteria for being a candidate endophenotype warrants attention. In previous work on this sample, we reported on several promising SAD endophenotypes, involving characteristics of brain structure and brain function, ,, as neuroimaging data from the LFLSAD supported the endophenotype criterion of co-segregation of the endophenotype with social anxiety within the families, and provided evidence for heritability. The Leiden Family Lab study on Social Anxiety Disorder (LFLSAD), which involved participants of two generations from families genetically enriched for SAD, was especially designed to examine neurobiological SAD endophenotypes. This is of particular importance in SAD, given the high prevalence of the disorder already in adolescence and the struggle to treat SAD effectively. As recently discussed, the application of the endophenotype-approach in psychiatry takes into account the notion that genes are ‘the biological bedrock of mental illness’, and as such they provide an important starting point to delineate the often complex pathophysiology of psychiatric disorders. Furthermore, an endophenotype should be heritable (criterion 3), and an endophenotype typically co-segregates with the disorder within a family, with nonaffected family members showing altered levels of the endophenotype when compared to the general population (criterion 4) – in other words: ‘the endophenotype is more prevalent among the ill relatives of ill probands compared with the well relatives of the ill probands’, which can be examined by exploring associations between symptoms and the hypothesized endophenotype within families. Endophenotypes should be associated with the disorder of interest (criterion 1) and are supposed to be stable, state-independent traits, already present in a preclinical state (criterion 2). A promising method to investigate the innate neurobiological susceptibility to SAD is the endophenotype approach, as endophenotypes are heritable, measurable characteristics on the pathway from genotype to phenotype,. Little is known, however, about the neurobiological variations underlying the genetic risk to SAD. In the present work, we focus on the innate vulnerability to develop SAD, as previous research demonstrated that SAD runs in families: several studies involving families or twins indicated that being ‘genetically close’ to a patient with SAD leads to an enhanced risk to develop the disorder, ,, and heritability estimates of SAD around 50 % have been reported.
This stresses the need for insight in the neurobiology underlying the development of SAD, in order to advance preventive interventions.
With its typical onset during childhood and early adolescence, ,, followed by a chronic course, suboptimal treatment and high rates of comorbid psychopathology, ,, the disorder is very incapacitating.
Patients with SAD fear a negative evaluation by others and avoid social situations as much as possible. Social anxiety disorder (SAD) is a prevalent anxiety disorder, ,, with serious and often life-long consequences for patients, their families and society.
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